This invention relates to a vehicle with an electric motor and more particularly to an improved electric motor assisted manually propelled vehicle.
There has been proposed a type of vehicle that is pedal operated, but which incorporates an electric motor for providing electric motor assist to the manual force input by the operator. This type of vehicle normally takes the form of a bicycle, but the principle may be used with a wide variety of types of manually powered vehicles.
Conventionally, the manual power is exerted on a pedal mechanism, and this pedal mechanism is coupled through a transmission including a free wheeling device to the driven wheel or wheels or other propulsion device for the vehicle. In addition, an electric motor is connected to the same propulsion device, but is operated only intermittently. An arrangement is provided for sensing the force exerted by the operator on the pedal mechanism, and then an electric power assist proportional to the manual input is added to the manual input for powering the vehicle.
This type of device has wide advantages and a great deal of utility. However, in accordance with the control arrangement and the various components of the system, there are some areas where improvements are possible. For example, there may be instances when the operator applies force to the pedal of sufficient magnitude to normally call for the application of electric power assist. However, the actual vehicle condition may be such that it would be unnecessary, and in fact undesirable, to supply electric power to the electric motor for assist.
It is, therefore, a principal object of the invention to provide an improved electrically assisted, manually operated vehicle wherein the electric assist is not applied even if the operator applies sufficient force to call for it unless the vehicle condition actually warrants power assist.
For example, the operator may actually stand on the pedals or apply force to them either when the brake is applied or when the vehicle is abutted against an object such as a wall or the like which makes forward motion impossible. If some arrangement is not provided for ensuring against electric power assist, electric power will be supplied to the electric motor by the batteries and the battery power will be depleted without the motor actually causing any operation of the vehicle.
It is, therefore, a further object of this invention to provide an improved arrangement for determining when the pedal operation actually calls for power assist from the vehicle condition and will only provide power assist when the vehicle condition warrants.
In addition to the aforenoted condition, there are times when the operator may change significantly the manual force applied to the propulsion device and where the system would normally provide substantial changes in electric power assist in response to such operator called for changes. However, if the power is suddenly changed, this can cause rather abrupt changes in speed of the vehicle, which may be undesirable in many instances.
It is, therefore, a still further object of this invention to provide an improved arrangement for controlling the application of power by the electric power assist when the operator changes significantly the force input so as to avoid abrupt changes in vehicle speed.
One condition under which such a rapid change of electric power assist may be undesirable is during initial start-up of the vehicle. When accelerating from standstill, the operator tends to place a larger force on the pedals than is required to maintain a constant speed. If this larger force is translated into an amplified electric power assist, then a jerky or abrupt start may result.
It is, therefore, a still further object of this invention to provide an improved power assist for a vehicle wherein the amount of power assist on start-up is reduced so as to reduce the likelihood of abrupt starts.
Even when traveling at steady-state speeds, the operator may decide to either accelerate or decelerate by changing the force that he applies to the pedal. If the power assist is changed at the same magnitude, then either abrupt acceleration or abrupt decelerations may result.
It is, therefore, a further object of this invention to provide an improved arrangement for controlling the amount of electric power assist in response to large variations in operator-applied force.
The disadvantages of applying large amounts of electric power to the electric motor for assist when the vehicle is stationary have been noted. Once the vehicle has been traveling under electric power assist, there may be instances where the running condition of the vehicle is such that power assist is no longer required. However, the vehicle condition or the operator input may be such that the control methodology would indicate that electric power assist is still required and would be provided.
It is, therefore, a still further object of this invention to provide an electrically assisted vehicle wherein the control for the vehicle determines when electric power assist is no longer required and shuts off the electric power under that condition.
As an example of when such a situation may occur, once the vehicle has been started and is traveling at speed, the operator may coast to a stop but still have some force applied to the pedals. If this occurs, then the electric power assist could come back on, and the vehicle might start. Alternatively, the power assist might be so small as to be insufficient to move the vehicle, but the operator would not notice the condition and the batteries could be discharged.
It is, therefore, a still further object of this invention to provide an improved electrically assisted vehicle wherein the power will be shut off at the appropriate time so that battery drainage will not result.
One type of control that has been proposed for use in electrically assisted vehicles incorporates an arrangement wherein the amount of power assist provided by the electric motor is varied in response to vehicle speed. Such arrangements are typically employed so as to prevent over-speeding of the vehicle through the use of the electric motor. Hence, some of these systems reduce the amount of power assist ratio as the speed of the vehicle increases. However, if the vehicle speed sensor is defective and does not provide a signal, then the entire control for the vehicle assist will be disabled.
It is, therefore, a still further object of this invention to provide an improved arrangement for determining when the speed sensor of an electric power assisted vehicle becomes inoperative.
In many of the desirable control routines which have been described, there are instances where for safety or other reasons the electric power may be discontinued. However, shutting off the electric power assist abruptly and without prior warning to the operator can give rise to some problems. For example, the operator may be in a condition where he would desire to know in advance that the electric power assist maybe is going to be shut off so as to cause certain operation of the vehicle and avoid sudden slowdown of the vehicle which might be unanticipated.
It is, therefore, a still further object of this invention to provide an improved electrically assisted vehicle wherein the power is shut off in response to certain conditions, but the operator is given an advance warning that the power will be shut off, and the power is not shut off until a predetermined time has elapsed.
As has been noted, the electric power assist is generated by an electric motor that is operated by a vehicle battery. There are instances, however, where the condition of the battery is such that it would be undesirable to provide electric power assist.
It is therefore, a still further object of this invention to provide an improved electric power assisted vehicle wherein the battery condition is checked periodically and electric power assist is not provided if the battery is not in a predetermined condition.
As an example of such a situation, the operator may either inadvertently or intentionally replace the battery with one having a higher voltage than the system was designed for. This could cause excessive speed of the vehicle and other problems.
It is, therefore, a yet further object of this invention to provide an electric power assisted vehicle wherein the electric power assist is precluded if the battery voltage is greater than a predetermined value.
Another condition where battery condition may be important is if the battery becomes depleted. The battery may still be at a level that it is capable of offering electric power assist, but it will be incapable of doing so in a short period of time. If the operator is not warned of this condition, then the battery power may be depleted, and the rider will not be able to have power assist when it is required.
It is, therefore, a still further object of this invention to provide an arrangement for an electric power assisted vehicle wherein the operator is warned of low battery voltage and the battery voltage is preserved during the warning time period.
In addition to the electric power motor assist for a manually operated vehicle, such vehicle's frequently carry other accessories that require battery power for their operation. Headlights and stop lights are an example of such auxiliary accessories that require electrical power. Although these accessories may be powered off of the same battery that powers the electric motor for power assist, there are many instances where this is not desirable or possible. For example, the electric motor may be designed to operate at a higher voltage than the other accessories. Furthermore, it may be desirable to insure that the battery for the power assist does not operate these accessories so as to prevent its becoming depleted. Thus, auxiliary batteries may be employed for the auxiliaries. However, these auxiliary batteries are small and may require frequent replacement which can cause problems.
It is, therefore, a further object of this invention to provide an electrically assisted vehicle having other electrically operated accessories that are operated by separate batteries but wherein those batteries may be periodically recharged from the main battery that powers the electric assist.